Many criticality accidents have been observed to emit a blue flash of light and to heat the material substantially. This blue flash or "blue glow" is often incorrectly attributed to Cherenkov radiation, most likely due to the very similar color of the light emitted by both of these phenomena. This is merely a coincidence.

Instead, the blue glow of a criticality accident results from the spectral emission of the excited ionized atoms (or excited molecules) of air (mostly oxygen and nitrogen) falling back to unexcited states, which happens to produce an abundance of blue light. This is also the reason electrical sparks in air, including lightning, appear electric blue. It is a coincidence that the color of Cherenkov light and light emitted by ionized air are a very similar blue despite their very different methods of production. It would be also interesting to remark that the ozone smell was said to be a sign of high radioactivity field through Chernobyl liquidators.

The only situation where Cherenkov light may contribute a significant amount of light to the blue flash is where the criticality occurs underwater or fully in solution (such as uranyl nitrate in a reprocessing plant) and this would be visible only if the container were open or transparent.